I just started posting recently, so sorry if this is a big repeat...but I'm 15 weeks with my first baby and cannot differentiate the difference.
I had these "pains" (which felt more like tickling) as early as 7-8 weeks but mainly down low and in one spot. I am now 15 weeks and they seem to feel somewhat the same but are in various places. They don't last but a few seconds but they're pretty constant. I had a 14 week scan done, recommended by my midwife, and the baby was doing some crazy karate moves lol so I know at this point it's all over the place. Just curious is 15 weeks is too early? I have no kids, no kids in my family, no friends that have been pregnant...I'm just a big fat newbie.

Re: Ligament Pain or Movement?
Based on previous postings on this topic, you will prob. get a lot of "15 weeks is too early to feel movement for a FTM", HOWEVER, I too felt quivering/tickling movement VERY early 13-14 weeks, was not sure it was baby at the time but now that I am 26 weeks I can say with certaintly that was him. The movements every woman feels seem to be different, but what you are describing sounds very similar to the way I felt - not pain per say but not the greatest feeling either.
Your 7-8 week feeling I would think had to be gas, baby was VERY tiny then.
As for ligament pain, you will know it when you feel it! OUTCH!!! Usually strikes when you get up too fast, sneeze, blow your nose.
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I have had that sharp pain when standing up, but this weird tickling sensation has happened from very early on and wasn't gas so, I guess I assumed that was ligament pain. I don't know anymore....I guess i'll just wait and I bet a baby comes out regardless.
I first started feeling fluttering around 12 weeks but couldn't really confirm it was the baby until it started getting stronger and more consistent at about 13/14 weeks.